Recent studies by the Chemical Industry Institute of Toxicology (CIIT) suggest that exposure to formaldehyde vapor may be carcinogenic in rats. These findings have raised concern for the health of 1.75 million workers with occupational exposures to formaldehyde as well as persons with exposure from home insulation. This proposal is to examine the mortality experience of pathologists, a medical specialty group with formaldehyde exposure, using a non-concurrent prospective study design. Comparison populations include other physician specialists who have had only limited exposure to formaldehyde. All causes of death listed on death certificates will be examined, and selected causes, notably cancers, will be verified. Industrial hygiene measures will be made to assess and rank both current and historical levels of formaldehyde exposure according to activities of pathologists. Professional activities of pathologists will be ascertained and a "dose," based on the industrial hygiene measures, will be assigned to each activity. A nested case-control study will be done to examine in more detail these pathologists' exposure to formadehyde. Data collected in other studies of physicians as well as from the case-control study will be used to adjust for any differences in possible confounding variables.